摘要:

AbstractKinetin has been shown to act synergistically with indole‐3‐acetic acid (IAA) or calcium ion (Ca2+) to stimulate ethylene production. Several commercially available cytokinins (kinetin, kinetin‐riboside, benzyladenine, benzyladenine‐riboside, isopentenyladenine, isopentenyladenine‐riboside, and zeatin) as well as noncytokinin bases (adenine and xanthine) were administered to mung bean (Phaseolus aureusRoxb.) hypocotyls to study their effects, alone or in combination with IAA or Ca2+, on ethylene production. In the presence of IAA or Ca2+, all cytokinins tested synergistically stimulated ethylene production and were as effective or nearly as effective as kinetin. Noncytokinin bases (adenine and xanthine) were, however, inactive in th

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1977.tb09275.x

出版商:Blackwell Publishing Ltd    

年代:1977

数据来源: WILEY

摘要:

AbstractExogenously applied 8‐14C‐kinetin is rapidly taken up by seeds of lettuce (Lactuca sativaL. cv. Grand Rapids). Radioactive metabolites were extracted and purified by solvent fractionation, column and paper chromatography. The primary metabolite was identified as the 9‐riboside‐5′‐monophosphate. As germination proceeds, some kinetin is released from this bound storage form, giving a maximum level of free kinetin at 12 hours after imbibition. After this time the concentration of ribotide increases while the concentration of free base decreases. Other metabolites are the 9‐riboside, AMP and IMP.It is suggested that a required amount of free base cytokinin is necessary by 12 hours after imbibition. This concentration of free cytokinin may act as a physiological trigger for later events durin

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1977.tb09276.x

出版商:Blackwell Publishing Ltd    

年代:1977

数据来源: WILEY

摘要:

AbstractA strain of carrot cells (Daucus carotacv. Kintoki) grew exponentially in the presence of 2,4‐dichlorophenoxyacetic acid (2,4‐D, 1 mg/1) with a doubling time of about 2 days. When those cells were transferred to a medium lacking 2,4‐D, they continued to grow at almost the same rate for about a week. When the cells were again transferred to the auxin‐free medium, the rate of cell division gradually decreased. After the cell division had ceased, cells were returned to the ordinary 2,4‐D medium. A burst of cell divisions occurred after about 2 days. Timing of DNA synthesis and of mitosis suggested that the cells had been arrested at G1phase. In a medium containing indoleacetic acid instead of 2,4‐D, the auxin was rapidly degraded and the culture was similarly synchronized as in the auxin‐o

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1977.tb09277.x

出版商:Blackwell Publishing Ltd    

年代:1977

数据来源: WILEY

摘要:

AbstractSpectroscopic Changes in the Chlorophyll a of Porphyridium Induced by Illumination and Chemical Action and Observed at −196°C.Photo‐oxidation of P700 by 708 nm light can take place under weak intensity (10−6W × cm−2) when the medium is frozen. Spectral characteristics of “700 nm” and “690 nm” variations are accurately measured. The amplitude of the photoinduced changes of absorption are similar to those induced by chemical action. In the case of Porphyridium, an apparent increase of the extinction power of P700 at −196°C is observed. This fact seems to be due to a diminution of the bandwith of the neighbouring pigments.Irradiation with red light (685 nm), of a relatively high intensity (10−2W × cm−2), in the presence of oxygen at −196°C, induces a slight shift (0.5 nm) of the red absorption band maximum towards longer wavelengths. This change is similar to the one promoted by ferricyanide in the dark. The origin and the functional significance of

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1977.tb09278.x

出版商:Blackwell Publishing Ltd    

年代:1977

数据来源: WILEY

摘要:

AbstractGibberellic acid was applied near the shoot apical region of rosettes ofVerbascum thapsus, a biennial weed, over a 6‐week period. Starch content and the activities of α‐amylase, β‐amylase, glucan phosphorylase and acid and alkaline phosphatase were determined for roots of the rosettes for 5 of the 6 weeks of gibberellin treatment. Starch content decreased during the first week of treatment, and it continued to drop until the third week, at which time virtually no starch remained. There was a concomitant increase in activities of the starch degradative enzymes, all of which reached their respective peaks of activities by the end of the second week of hormonal treatment. The peaks of these enzymatic activities occurred approximately 1 week before appearance of the first morphological signs of bolting. Alkaline phosphatase showed an early response to applied gibberellin, and its peak of activity coincided with early signs of

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1977.tb09279.x

出版商:Blackwell Publishing Ltd    

年代:1977

数据来源: WILEY

摘要:

AbstractA theoretical model for photoperiodic time measurement in higher plants is presented. It is based on the concept that the diurnal change in responsiveness to the phytochrome pigment system is dependent upon a circadian rhythm in membrane functioning and configuration, which is reflected in a parallel rhythm in membrane binding capacity for phytochrome Pfr. Phytochrome in turn, being an integrated part of the membrane clock, is acting as a “Zeitgeber” by mediating the external light stimuli in phase‐controlling of the membrane oscillation. Phytochrome and the circadian clock is thus integrated into one structural and functional unity.Applied to the field of photoperiodic control of flowering the model is shown to account for most of the conflicting experimental results in both short‐day and long‐d

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1977.tb09280.x

出版商:Blackwell Publishing Ltd    

年代:1977

数据来源: WILEY

摘要:

AbstractThe translocation and metabolism of ethephon at pH 7.0 and its effect on abscission of olive fruit, were studied in attached and detached fruits. In detached olives, the lowest fruit removal force values were achieved when the fruits were treated at their proximal cavity and kept under humid conditions. Following application of14C‐ethephon to the proximal cavity 63% of the label was absorbed within 4 h; evolution of14C‐ethylene proceeded at a slow rate, mainly from14C‐ethephon remaining on the olive surface, totaling 37% of the applied ethephon in 20 days.14C‐ethephon disappeared rapidly after its application to olive on the tree. More14C‐ethephon could be extracted from olives on the trees after distal application than after proximal application.Since the response of detached olives to treatments with ethephon was similar to that of attached olives in regard to fruit removal force reduction, the former can be used for the study of many aspects of ethephon and ethylene metabolism in olives.In our study no ethephon metabolites other than14C‐ethylene could be detected after14C‐ethephon application to attached or detached

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1977.tb09281.x

出版商:Blackwell Publishing Ltd    

年代:1977

数据来源: WILEY

摘要:

AbstractThe fungusFusarium oxysporumSchlecht f. sp.tulipaeApt. can produce ethylene abundantlyin vitrowhen grown in Pratt's liquid medium with glucose as the only organic substrate. This production starts after a lag phase of about 4 days, and peak production occurs when mycelium weight has reached its maximum value. For several days the rate of production is more or less linearly dependent on pO2. The total production is also dependent on the oxygen concentration, but pure oxygen inhibits the total production by about 50% as compared with 21% oxygen. The high production in shake cultures, as compared with the low production in stagnant cultures, is probably the result of a better oxygen supply in the culture medium. The mycelium weight proved not to be a valid referential basis for the production of ethylene.

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1977.tb09282.x

出版商:Blackwell Publishing Ltd    

年代:1977

数据来源: WILEY

摘要:

AbstractA membrane‐bound and a soluble cyclic nucleotide phosphodiesterase from sunflower callus has been examined. Kinetic studies showedKm‐values in the range of 2.5‐5.0 mMwith cyclic adenosine 3′,5′‐monophosphate (3′, 5′‐cAMP) as the substrate. The soluble cyclic nucleotide phosphodiesterase was characterized further: Optimal activity was at pH 6.5‐7.0 and at 40°C. The enzyme did not require divalent metal ions for maximal activity. It was inhibited by Cu2+and slightly activated by Fe3+. Sodium fluoride, imidazole and theophylline did not affect the activity, but caffeine was slightly inhibitory. Its activity was strongly inhibited by ATP, AMP and Pi. The enzyme hydrolysed 3′,5′‐cAMP, 2′,3′‐cAMP and 3′,5′‐cGMP, while N6, O2′‐dibutyryl cyclic AMP (dBcAMP) was left unattacked. The soluble enzyme activity was influenced neither by callus age nor by plan

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1977.tb09283.x

出版商:Blackwell Publishing Ltd    

年代:1977

数据来源: WILEY

摘要:

AbstractABA inhibits the germination of Grand Rapids lettuce seeds at a temperature at which photoblastism is not observed. This ABA inhibition can be overcome by GA, or cytokinin, or red light acting alone or in concert. At high levels of ABA the ameliorative effects of GA, cytokinin or red light are not manifest and it is suggested that lettuce seeds' response to a given level of ABA is temperature dependent, and any interaction which may be observed between ABA and other regulators, or red light, likewise is temperature dependent.Seeds only actively metabolize ABA after germination is complete though ABA does influence the germination process proper. Some radioactivity, originally applied as14C ABA, cannot be extracted from14C ABA treated seeds by methanol, and this “fixed” ABA can constitute more than 50% of the activity taken up by the seeds. High levels of “fixed” ABA are found in seeds which do not germinate. As well as this “fixed” ABA two labelled metabolites arise in seeds treated with14C ABA. The levels of these rise in seed extracts as the level of extractable ABA decreases.Whilst ABA can affect germination our results do not allow us to assign a specific regulatory role to ABA in seed

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1977.tb09284.x

出版商:Blackwell Publishing Ltd    

年代:1977

数据来源: WILEY